Process of treating hydrocarbon oils



Oct. 5, 1937.

' W. A. CRAIG PROCESS OF TREATING HY-DROCARBON OILS Filed June 30. 19362 Sheets-Shea?l l f O $58 SN oww A TTORNE Oct. 5, 1937. S w. CRAIG2,094,586

PROCESS OF TREATINGHYDROCARBON OILS Filed June 50, 1936 2 sheets-sheet 2F/cJ- WMM L 615.44m

ATTORNEY Patented Oct. 5, 1937 UNl'lE .STATES rincones or rnsarrnanrDnocAnBoN ons Application .lune Si), 1,936, Serial No. 88,100

i Claims.

This invention pertains to an improved system 'or method oi treating,purifying and refining hydrocarbon oils with maintained aqueoussolutions of metallic salts. More specifically, this invention pertainsto improving the treating characteristics of metallic salt solutions inorder to maintain deiinite concentrations thereof at the best or moredesired treating temperatures, when used to purify and rene mineralhydrocarbon oils in'vapor phase, such as gasoline or naphtha, or otherpetroleum oil products derived by distillation Yor cracking of mineraloils.

Treatment of hydrocarbon oils in vapor phase with maintained aqueoussolutions of metallic salts is generally knownY in the reiining art, in

which the degree of renement by the treatment is determined, in part, bythe concentration of the metallic salt maintained in the liquid phase,and the desired concentration of the treating Vsolution has beengenerally controlled primarily by controlling the temperature of thesystem` and -the partial pressure of the Water in the vapor phase. n Y YMy invention is an improvement in the method described in U. S. Patent#1,790,622, granted to Arthur Lachman, dated January'Z'l, 1931, forMethod of rening mineral cils, and U. S. Patent #1,809,170, granted toArthur Lachman, dated 1 June 9, 1931, forpProcess of refininghydrocarbons, which disclose methods of refining hydrocarbon oils invapor phase With Water solutions of the metallic salts ci `zinc, copper,cadmium, mercury, iron, chromium, manganese, aluminum, nickel or cobalt,Which may be the chloride, bromide, sulphate, nitrate, and also any ofthe Water soluble salts of the above named metals of organic acids, suchasl the sulphonic acid of benzol, toluol,

Xylol, or the sulpho acids derived from the treatment oiV petroleum oilswith sulphuric acid.

The method described in the aforesaid patents for refining oilcomprises, passing the oil, such as gasoline stock, in Vapor phasethrough and in Contact With a hot water solution of any of the aforesaidmetallic salts, in which a tower iilled'v with contact material and asubstantially concentrated water solution ofthe metallic salt isemployed.

While it is possible to maintain any desired concentration of themetallic salt in the liquid phase by the proper choice of temperatureand vpartial pressure of Water vapor, the operating conditions duringthe treatment of a light petroleum distillate, such as naphtha stocks,are restricted by the characteristics of the latter. In order tomaintain the distillate or naphtha stock (Cl. Lilli-36) in vapor phaseduringtreatment, certain conditions Yoi temperature and vapor pressuremust be observed. 1 It is necessary, therefore, to choose operatingconditions that will maintain the concentration of the salt solution atthe desired strength and at the same time maintain the distillate ornaphtha stock under treatment in vapor phase. The treatment ofhydrocarbon mixtures containing unsaturated hydrocarbons with metallicsalt solutions causes some of the latter to polymerite or condense toform materials of higher mclecular Weight. The characteristics of thepolymers and condensed materials depends upon the characteristics of theoriginal unsaturates and the severityoi treatment, and it has beenobserved that some of the reaction products are recovered lin thegasoline fraction, While others are removed in the higher boilingportions of the discharged material,V Fractionation will effect theremoval of high-boiling polymers and allow the recovery oi a treateddistillate having favorable characteristics, such as good color, goodcolor stability when exposed to sunlight, absence of gums and gumforming constituents, etc.

There are times when it is beneficial to maintain the salt solution at arelatively low concentration. If it becomes desirable to lower theconcentration within the treating vessel, it may be accomplished bylowering the temperature or increasing the partial pressure oi the waterin the vapor phase, or both. However, such changes also affect theliquid-vapor equilibrium of the hydrocarbon oil, as shown in thefollowing Table No. l, which illustrates some of the varying treatingconditions which may be employed in purifying a cracked gasoline stock.

Under the chosen conditions, as shown incolumn l of Table No. 1, a zincchloride concentration of 82.5% is obtained, and the hydrocarbon oil invapor phase has an average boiling point of approximately 330 F. If theconditions of pressure and Water Vapor pressure are maintained but thetemperature is lowered to 335 F., as shown in column 2, the Zincchloride concentration will be reduced, and at the same time the averageboiling point of the hydrocarbons will be reduced, and a portion of thehydrocarbons which Were formerly in vapor phase will condense Within thetreater.

Column 3 shows the effect of changing the proportion of water vaporwithin the treater and maintaining the temperature and pressureconstant. Such a change Will reduce the Zinc chloride concentration ofthe treating solution and increase the average boiling point of thehydrocarbons in vapor phase, provided, of course, that there are.hydrocarbons present in liquid phase to allow this increase to takeplace.

Column 4 shows the conditions necessary to reduce the zinc chlorideconcentration, and at the same time maintain the. average boiling pointof the hydrocarbons in vapor phase at approximately the same value asthat shown in column 1. It is, therefore, evident that conditions oftemperature, pressure and Water vapor pressure can be chosen so that theconcentration of Zinc chloride in solution and the average boiling pointof the hydrocarbons in vapor phase can be controlled to a limitedextent. The same sort of control can be achieved if other treatingreagents are used when the characteristics of the treating solution areknown. It is seen that:-

l. Temperature reduction decreases the concentration of the metallicsalt solution;

2. Temperature reduction decreases the average boiling point of thehydrocarbons in the vapor phase;

3. Increase in water vapor pressure decreases the concentration of themetallic salt solution;

4. Increase in water vapor pressure increases the average boiling pointof the hydrocarbons in the vapor phase.

From an economical point of View, it is desirable to reduce the steamrequirements of the treating system to a minimum. It is shown in theabove discussion, however, that higher temperatures would be required tooffset the effect of reduced water Vapor pressure upon the averageboiling point of the hydrocarbons in the vapor phase. These conditionswould affect the treating solution, causing it to become more.concentrated. Inasmuch as the severity of treatment depends in part uponthe concentration of the metal salt, it is evident that high temperatureand minimum steam addition will give` more severe treatment than willoccur with lower teinperature and greater additions of steam. Somehydrocarbons are adversely aiected by severe treatment, and it isnecessary to subject stocks of this nature to the milder action of moredilute reagents. One is, therefore., required to sacrice economy insteam consumption in order to avoid over-treatment of such materials.

Now I have discovered that, in the refining of vaporized hydrocarbonssuch as naphtha or gasoline stocks with aqueous zinc chloride and otherlike metal salt treating solutions, the aforesaid difficulties may beovercome by dissolving inthe treating solution certain compounds whichwill decrease the vapor pressure of the treating solution at a giventemperature, or modify the ternperature-vapor pressure-concentrationrelationship. Such compounds, used by my invention to modify thetemperature-vapor pressure-concentration relationship, may be inert ornon-reactive salts which are soluble in the treating solution, such ascalcium chloride, sodium chloride, potassium chloride, and the like,dissolved in treating solutions of zinc chloride, copper chloride,aluminum chloride, and the like, as described in my pending applicationSerial No. 60,039, led January 21, 1936, for Process of treatinghydrocarbon oils.

In treating solutions made from metal sulphate salts, such as Zincsulphate, copper sulphate, etc., d

non-reactive salts would be employed to modify the temperature-vaporpressure-concentration relationship, such as sodium sulphate, potassiumsulphate, and the like, to avoid reactions which would causeprecipitation, or removal of any of the components of the treatingsolution.

I have further discovered that soluble organic salts of the pyridinetype will also modify the temperature-vapor pressure-concentrationrelationship of treating solutions. These compounds may be pyridine,pyridine homologues, or the nitrogen base compounds extracted frompetroleum oils, which may be added to the treating solution in the formof bases and allowed to react with the acid which is formed byhydrolysis of the. metal salt treating agent, or these nitrogen basesmay be converted into salts by the addition of acid, such, for example,as by the addition of hydrochloric acid to produce hydrochlorides, andthen added in this form to the metal salt treating solution.

The following Table. No. 2 illustrates the changes in the boiling pointsproduced by the addition of petroleum base hydrochlorides to zincchloride treating solution, and the saving in steam eiected thereby inrefining gasoline stocks.

TABLE No. 2

Comparison of treating characteristics of eine chloride solution andeine chloride solution containing petroleum base hydrochlorides haring aratio of base to eine chloride of 0.090

ZDC12 ZIlClg ZIlClz ZIlClz ZDCIQ and base and base and base and base andbase Treating solution ZnClg hydro- ZnClg hydro- ZnCl2 hydro- ZnClzhydro- ZnCl2 hydrochlochlochlochlo- 0h10. rides rides rides rides ridesTreating temp-ur 335 335 335 335 335 335 35o 35o 379 379 Treatingpressure-lb/sq. in. abs. 40 40 33 33 33 33 40 40 40 40 Mol. percentwater in vap0rS 36. 7 36.7 23. 5 23. 5 44. 2 44. 2 22.5 22.5 36. 7 36. 7Abs. vapor pres. of Water lb./sq. f in 14. 7 14. 7 7. 75 7. 75 14. 7 14.7 9. 0 9. 0 14. 7 14. 7 Abs. vapor pres. of hydrocarbon 1b./sq. in 25.325. 3 25.3 25.3 18. 3 18. 3 31. 0 31. 0 25.32 25. 32 Concentration ofZnClz wt. percent 80 74. 6 85 80 80 74. 6 87 80 86. 4 80 Av. boiling pt.at l atmos. of

hydro. in vapors aF 295 295 295 295 320 320 295 295 340 340 Steamrequired per bbl. hydro 22. 35 22. 35 12.05 12. 05 30. 5 30V 5 11.3 11.322.35 22. 35.

F`Ialole No. 2 shows thatat constant conditions of temperature, pressureandV partial pressure of water vapor, the zinc'chloride concentration islowered by the addition of petroleum base hydrochlorides. At constantzinc chloride concentration, the presence of bases allows operation atlower pressures, or lower partial pressure of water Vapor. At constantzinc chloride concentration, constant pressure and constant partialpressure of water vapor, higher temperatures can be employed.

An object of the invention is to renehydrocarbons in vapor phase at agiven temperature, with a water solution of a metallic salt, at adesired vapor pressure.

Another object ofthe invention is to refine hydrocarbons in'vapor Aphaseat a given temperature, with a water Vsolution of a metallic salttreating agent, maintained at av desired vapor pressure by the additionof an inert compound which is soluble in the treating solution.

Another object of the invention is to refine hydrocarbon oil Vapor bycontact with a reactive salt solution containing a relativelynon-reactive salt or compound dissolved therein, in quantitiessufficient to modify the temperature-vapor pressure-concentrationrelationship of the solution to the desired degree.

Various other objects and advantages of the present invention scriptionof the preferred form or example of the method embodying'the invention;For this purpose reference is made to the yaccompanying drawings.

Figure I shows the relationship at atmospheric pressure of boiling pointand concentration of aqueous Zinc chloride solutions in which varyingamounts of nitrogen base hydrochlorides are dissolved. The ratios shownin the legend on the figure are calculated from the content of freebases rather than the content of base hyrochlo-V ride. Each curverepresents a constant ratio of nitrogen bases to Zinc chloride. Similarcurves can be prepared to show the same relationship at pressures otherthan atmospheric, or for other treating solutions.

Figure II represents which the invention may I represents a treater forcontacting hydrocarbon oil vapor with refining agent. The lower sectionof treater I is filled with bubble cap trays generally apparatus in beperformed, in which 2, and provided with a compartment trap 3 stationedabove the last tray or row of bubble caps. Pipe 4, controlled by valve5, connects treater I f near the bottom to a source of hydrocarbon vaporto be treated, such as a fractionating column, still, or other form ofvaporizer. Pipe 6, controlled by valve 'I, connects hydrocarbon vaporpipe 4 to a source of the treating solution. Pipe 8, controlled by valve9, connects pipe 4 to a source of steam. Pipe II), controlled by valveII, connects treater I at the bottom to a storage for waste supply, notshown. Pipe I2, controlled by valve I3, connects the compartment trapsection of treater I to a source of steam. A discharge pipe I4,controlled by valve I5, connects the compartment trap section of treaterI to a storage for spent treating solution, not shown. Pipe I6 connectstreater I at the top to allow the vapors to pass to other equipment forfurther processing, known in the art.

The preferred operation as carried out in the apparatus just described,is as follows: y

The treating solution is preferably a water solution of zinc chlorideand petroleum base hydrowill be apparent from the de-V chlorides, inwhich the ratio:l of petroleum bases to zinc chloride ranges fromabout0.09 to 0.65 part by weight of petroleum bases to 1 part by weight ofzinc chloride. While the preferred salts employed to make the treatingsolution are zinc chloride and petroleum base hydrochlorides, it is tobe understood that anyof the other salts or mixtures thereof andcompounds heretofore enumerated may be used in like manner at` variousratios and concentrations to suit the oil to be treated and the productdesired. However, in order to simplify this example, the conditionswhich arepresented in columns l and 2 of Table No. 2 will be used toillustrate my improved meth- ,od of operation.

Treater I is first lledup to the level of the dischargepipe I4 with thetreating solutionto be employed, heated to a desired temperature,preferably ranging from about 360 to 390 F., by a heaterv not shown,which discharges the heated solution through pipe 6, controlledk byvalvel, pipe d, and into said treater I near the bottom.

Hydrocarbon oil vapor, such as gasoline or naphtha stock, coming fromany of the known refinery vaporizers, orvaporizer and fractionating`system, at or above the vapor temperatureof the stock to be treated,passes through pipe 4, controlled by valve 5, and into the lower sectionof treater I. At the same time a regulated quantity of steam, requiredtemperature so as to maintain the oil vapor atfany required treating,temperature,is continuously passed into the cil vvapor passing throughpipe 4, the steam coming through pipe, controlled by valve 9. Thetreating solution may also be continuously or intermittently introducedinto pipe 4 through pipe 6, controlled by valve 1, in quantitiessufficient to maintain the treating solution in treater I at therequired strength and purity tol continuously effect uniform treatmentof the oil vapors.

The hydrocarbon vapors, commingled with steam, pass from pipe 4 intotreater I, and are therein intimately contacted with treating solutionand treated to the required degree'as they pass up through the bubblecap tray system 2. The contents of the treater are kept at a temperatureof 335 F., a pressure of 40 pounds per l square inch absolute, and anabsolute water-val por pressure of 14.7 pounds per square inch.

Under these conditions, the aqueous treating solution will containapproximately 74.6 by weight of Zinc chloride, and petroleum basehydrochloride, calculated as free bases, amounting to about 6.7%. Thehydrocarbons in Vapor phase will be foundy to have an average boilingpoint of approximately 295 F. It might be pointed out at this time that,under identical conditions within the treater except that the petroleumbases be absent, the concentration of Zinc chloride in the solutionwould be approximately 80%, as shown in column l of Table No. 2.

The spent or partially spent treating solution is continuously orintermittently discharged from treater I through pipe I4, controlled byvalve I5, to a storage tank not shown, and may be thereafter recoveredfor reuse by known methods. Steam may also be introduced into the uppersection of treater I through pipe I2, controlled by valve I3, tomaintain the oil in vapor phase. From treater I, the treated oil vaporsand gaseous products of reaction pass through pipe I6 to other equipmentknown in the art, in which the purified hydrocarbons are separated fromundesirable products of reaction.

which may be superheated to any f Cil ouV

The novel feature of my invention is the use of petroleum basehydrochlorides, or other inert compounds, to alter the concentration ofthe active metallic salt in the treating solution, so that greaterflexibility of operation may be obtained. By their use, lowerconcentrations can be obtained under constant operating conditions, orhigher temperature can be employed Without increasing the concentration,and thereby reduce the consumption of steam.

While the process herein described is well adapted for carrying out theobjects of the present invention, it is to be understood that variousmodifications and changes may be made without departing from the spiritof the invention, such, for example, as the use of other forms ofcontact towers or mechanical mixers, and the invention includes all suchmodifications and changes as appear within the scope of the appendedclaims. It also includes the treatment of normally gaseous unsaturatedhydrocarbons, by which they can be converted to hydrocarbons of greatermolecular weight. By means of my invention it is possible to increasethe treating temperature to a marked extent, and still maintain theactive treating material as a mobile aqueous solution, and at the sametime maintain a relatively low pressure upon the treating vessel.

I claim:

1. A method of rening hydrocarbon oil vapor Which comprises, contactingthe oil vapor mixed with steam at refining temperatures With aqueous,reactive, maintained salt solution of a heavy metal Vcontainingpetroleum base salts dis- Y chloride salts derived from petroleum oils.

3. In the process of rening hydrocarbon oil vapor mixed With steam, byContact with a Water solution of Zinc chloride at rening temperatures,maintained at constant concentration, constant pressure and constantWater vapor pressure, the improvement of maintaining a higher treatingtemperature by adding to the zinc chloride solution salts of petroleumbases, in amounts suii'icientv to refine the oil vapor at a requiredtreating temperature; Y

4. In the process of rening hydrocarbon oil vapor mixed with steam, bycontact With a water solution of zinc chloride at reining temperatures,maintained at constant concentration, constant pressure and constantWater vapor pressure, the improvement as in claim 3 in which thepetroleum base salts are hydrochlorides.

WALLACE A. CRAIG.

